79 results on '"David R. Silva"'
Search Results
2. HST Low-resolution Stellar Library
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Tathagata Pal, Islam Khan, Guy Worthey, Michael D. Gregg, and David R. Silva
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Hubble Space Telescope ,Stellar chromospheres ,Astrophysics ,QB460-466 - Abstract
In order to provide fundamental stellar spectra that extend into the UV, Hubble Space Telescope’s Space Telescope Imaging Spectrograph targeted 556 stars via proposals GO9088, GO9786, GO10222, and GO13776. Exposures through three low-resolution gratings provide wavelength coverage from 0.2 < λ < 1 μ m at λ /Δ λ ∼ 1000. The UV grating (G230LB) scatters red light that results in unwanted signal, especially in cool stars. We applied scattered-light corrections and flux corrections arising from pointing errors relative to the center of the 0.″2 slit based on Worthey et al. We present 513 fully reduced stellar spectra, fluxed, dereddened, and cross correlated to zero velocity. Because of the broad spectral range, we can simultaneously study H α and Mg ii λ 2800, indicators of chromospheric activity. Their behaviors are decoupled. Besides three cool dwarfs and one giant with mild flares in H α , only Be stars show strong H α emission. Mg2800 emission, however, strongly anticorrelates with temperature such that warm stars show absorption and stars cooler than 5000 K universally show chromospheric emission regardless of dwarf/giant status or metallicity. Transformed to Mg2800 flux emerging from the stellar surface, we find a correlation with temperature with approximately symmetric astrophysical scatter. Previous work had indicated a basal level with asymmetric scatter to strong values. The discrepancy is primarily due to our improved treatment of extinction. We confirm statistically significant time variability in Mg2800 strength for one star.
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- 2023
- Full Text
- View/download PDF
3. The Astrophysical Events Observatories Network (AEON)
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Cesar Briceno, Alice Hopkinson, Stephen T. Ridgway, Stephen Heathcote, David R. Silva, Edward Gomez, Elizabeth Heinrich-Josties, John P. Blakeslee, Rachel Street, Bryan W. Miller, Jay Elias, Chien-Hsiu Lee, Andy Adamson, Mark Bowman, Lisa J. Storrie-Lombardi, Robert Blum, Todd Boroson, Adam S. Bolton, and Jon Nation
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User driven ,Telescope ,Fully automated ,Computer science ,Aeon ,law ,Time allocation ,Astrophysical Phenomena ,Soar ,Data science ,Scheduling (computing) ,law.invention - Abstract
Astrophysical phenomena occur on a range of timescales, and to properly characterize them, observations must be made at appropriate intervals on instrumentation determined by the scientific goals of the study. The traditional model of scheduling telescope time in blocks of consecutive nights and requiring the investigators to operate the instrument (either in person or remotely) is not optimal for this science. A queue-scheduled approach to time allocation can relieve the personal and financial burden of interactive observing runs. This is particularly powerful when requests for observations can be made through a programmatic interface, which provides not just a convenient tool for all astronomy programs, but also the opportunity to build fully automated observing programs. This will be an essential component of projects making follow-up observations for modern surveys that produce millions of alerts per night, as much of the science return will depend upon obtaining classification and characterization data rapidly and efficiently, as well as for coordination of observations across multiple facilities. The AEON Network is an initiative to build a programmatically accessible, queue-scheduled and user driven network of telescopes ideal for modern astronomical observing programs.
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- 2020
4. Building International Indigenous People’s Partnerships for Community-Driven Health Initiatives
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Wahbe, Tanya R., Jovel, Eduardo M., García, David R. Silva, Llagcha, Vicente E. Pilco, and Point, N. Rose
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- 2007
- Full Text
- View/download PDF
5. The ANTARES Astronomical Time-Domain Event Broker
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Shuo Yang, John Kececioglu, Zhenge Zhao, Benjamin Hauger, David R. Silva, N. Wolf, Chien-Hsiu Lee, Abhijit Saha, Adam S. Bolton, P. Aleo, Thomas Matheson, Navdeep Singh, Carlos Scheidegger, C. Stubens, Monika Soraisam, Richard T. Snodgrass, Eric Evans-Jacquez, Zhe Wang, A. Scott, and Gautham Narayan
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Physics ,010504 meteorology & atmospheric sciences ,Event (computing) ,business.industry ,Real-time computing ,Process (computing) ,FOS: Physical sciences ,Astronomy and Astrophysics ,01 natural sciences ,Annotation ,Software ,Data model ,Space and Planetary Science ,0103 physical sciences ,Time domain ,User interface ,business ,Astrophysics - Instrumentation and Methods for Astrophysics ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences ,Time domain astronomy - Abstract
We describe the Arizona-NOIRLab Temporal Analysis and Response to Events System (ANTARES), a software instrument designed to process large-scale streams of astronomical time-domain alerts. With the advent of large-format CCDs on wide-field imaging telescopes, time-domain surveys now routinely discover tens of thousands of new events each night, more than can be evaluated by astronomers alone. The ANTARES event broker will process alerts, annotating them with catalog associations and filtering them to distinguish customizable subsets of events. We describe the data model of the system, the overall architecture, annotation, implementation of filters, system outputs, provenance tracking, system performance, and the user interface., 24 Pages, 8 figures, Accepted by AJ
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- 2020
6. Divisions Panel Discussion: Astronomy for Development
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David R. Silva, Anna Wolter, Edward Guinan, Kevin Govender, Yihua Yan, E. F. van Dishoeck, Mary Kay Hemenway, and Nader Haghighipour
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Engineering ,Space and Planetary Science ,business.industry ,Astronomy and Astrophysics ,Engineering ethics ,Astrophysics ,business ,Panel discussion - Abstract
The main purpose of this panel discussion was to encourage conversation around potential collaborations between the IAU Office of Astronomy for Development (OAD) and IAU Divisions. The discussion was facilitated by the OAD and the conversation revolved mainly around two questions: (i) What should the OAD be doing to enhance the work of the Divisions? (ii) What could the Divisions (both members and respective scientific discipline in general) contribute towards the implementation of the IAU strategic plan?
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- 2015
7. Revised Stellar Properties of Kepler Targets for the Q1-17 (DR25) Transit Detection Run
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Fabienne A. Bastien, David R. Ciardi, Savita Mathur, Gilbert A. Esquerdo, Steve B. Howell, Lars A. Buchhave, David W. Latham, William D. Cochran, Daniel Huber, Andrew W. Howard, Howard Isaacson, Elise Furlan, Allyson Bieryla, Michael Endl, Natalie M. Batalha, David R. Silva, and Phillip J. MacQueen
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fundamental parameters [stars] ,FOS: Physical sciences ,Astrophysics ,LOW-MASS STARS ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Kepler ,CIRCLE-PLUS PLANET ,Planet ,0103 physical sciences ,distances [stars] ,Astrophysics::Solar and Stellar Astrophysics ,Transit (astronomy) ,010303 astronomy & astrophysics ,planetary systems ,Solar and Stellar Astrophysics (astro-ph.SR) ,SUN-LIKE STAR ,Astrophysics::Galaxy Astrophysics ,Physics ,Earth and Planetary Astrophysics (astro-ph.EP) ,SOLAR-TYPE STARS ,010308 nuclear & particles physics ,SOPHIE VELOCIMETRY ,MULTIPLE-PLANET SYSTEMS ,Astronomy and Astrophysics ,Radius ,Planetary system ,Exoplanet ,Weighting ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,evolution [stars] ,CANDIDATE HOST STARS ,F-TYPE STARS ,INFLATED HOT JUPITER ,Astrophysics::Earth and Planetary Astrophysics ,catalogs ,M DWARF STARS ,Astrophysics - Earth and Planetary Astrophysics - Abstract
The determination of exoplanet properties and occurrence rates using Kepler data critically depends on our knowledge of the fundamental properties (such as temperature, radius and mass) of the observed stars. We present revised stellar properties for 197,096 Kepler targets observed between Quarters 1-17 (Q1-17), which were used for the final transiting planet search run by the Kepler Mission (Data Release 25, DR25). Similar to the Q1--16 catalog by Huber et al. the classifications are based on conditioning published atmospheric parameters on a grid of Dartmouth isochrones, with significant improvements in the adopted methodology and over 29,000 new sources for temperatures, surface gravities or metallicities. In addition to fundamental stellar properties the new catalog also includes distances and extinctions, and we provide posterior samples for each stellar parameter of each star. Typical uncertainties are ~27% in radius, ~17% in mass, and ~51% in density, which is somewhat smaller than previous catalogs due to the larger number of improved logg constraints and the inclusion of isochrone weighting when deriving stellar posterior distributions. On average, the catalog includes a significantly larger number of evolved solar-type stars, with an increase of 43.5% in the number of subgiants. We discuss the overall changes of radii and masses of Kepler targets as a function of spectral type, with particular focus on exoplanet host stars., 19 pages, 13 figures. ApJS in press
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- 2016
8. Front Matter: Volume 9910
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David R. Silva and Roger Brissenden
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010308 nuclear & particles physics ,Observatory ,Political science ,0103 physical sciences ,Coordination network ,Library science ,010303 astronomy & astrophysics ,01 natural sciences - Abstract
Cooperating Organizations AAS—American Astronomical Society (USA) • ASJ—Astronomical Society of Japan (Japan) AURA—Association of Universities for Research in Astronomy, Inc. (USA) • Ball Aerospace & Technologies Corporation (USA) • CNRS—Centre National de la Recherche Scientifique (France) • EAS—European Astronomical Society (Switzerland) • ESO—European Southern Observatory (Germany) • IAU—International Astronomical Union (France) • INSU—Institut National des Sciences de l’Univers (France) • LAM—Laboratoire d’Astrophysique de Marseille (France) • MPE—Max-Planck-Institut fur extraterrestrische Physik (Germany) NAOJ—National Astronomical Observatory of Japan (Japan) • NASA—NASA Goddard Space Flight Center (USA) • Northrop Grumman Corporation (USA) • OAMP—Observatoire Astronomique de Marseille Provence (France) • OPTICON—Optical Infrared Coordination Network (United Kingdom) • RadioNet—Advanced Radio Astronomy in Europe (United Kingdom) • Royal Astronomical Society (United Kingdom) • Science & Technology Facilities Council (United Kingdom) • SFO—Societe Francaise d’Optique (France) Competitiveness Cluster: POPsud-Pole Optique & Photonique (France) • Optitec Sud (France)
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- 2016
9. ERRATUM: Revised Stellar Properties of Kepler Targets for the Q1–17 (DR25) Transit Detection Run (ApJS, 229, 30)
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Daniel Huber, David R. Ciardi, Michael Endl, Gilbert A. Esquerdo, Howard Isaacson, William D. Cochran, Elise Furlan, David R. Silva, Natalie M. Batalha, Fabienne A. Bastien, David W. Latham, Savita Mathur, Steve B. Howell, Allyson Bieryla, Lars A. Buchhave, Phillip J. MacQueen, and Andrew W. Howard
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Physics ,010504 meteorology & atmospheric sciences ,Space and Planetary Science ,0103 physical sciences ,Astronomy ,Astronomy and Astrophysics ,Transit (astronomy) ,010303 astronomy & astrophysics ,01 natural sciences ,Kepler ,0105 earth and related environmental sciences - Published
- 2018
10. EVIDENCE FOR INTERMEDIATE-AGE STELLAR POPULATIONS IN EARLY-TYPE GALAXIES FROM K -BAND SPECTROSCOPY
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Harald Kuntschner, Nicolás Cardiel, Scott Trager, Javier Gorgas, David R. Silva, A. Vazdekis, Reynier Peletier, E. Mármol-Queraltó, A. J. Cenarro, Patricia Sanchez-Blazquez, Kapteyn Astronomical Institute, and Astronomy
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Astrofísica ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Metallicity ,Population ,MU-M ,FOS: Physical sciences ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,S0 GALAXIES ,cD ,Base (group theory) ,ELLIPTIC GALAXIES ,GLOBULAR-CLUSTERS ,galaxies: formation ,NITROGEN ABUNDANCES ,Astrophysics::Solar and Stellar Astrophysics ,galaxies: elliptical and lenticular ,Fornax Cluster ,education ,Spectroscopy ,LOW-DENSITY ENVIRONMENTS ,Astrophysics::Galaxy Astrophysics ,CALIBRATION ,Physics ,education.field_of_study ,Star formation ,Física atmosférica ,Astronomy and Astrophysics ,FORNAX CLUSTER ,Galaxy ,Astronomía ,Stars ,galaxies: clusters: general ,Space and Planetary Science ,galaxies: elliptical and lenticular, cD ,galaxies: stellar content ,Astrophysics::Earth and Planetary Astrophysics ,galaxies: evolution ,METALLICITY ,Astrophysics - Cosmology and Nongalactic Astrophysics ,LICK INDEXES - Abstract
The study of stellar populations in early-type galaxies in different environments is a powerful tool for constraining their star formation histories. This study has been traditionally restricted to the optical range, where dwarfs around the turn-off and stars at the base of the RGB dominate the integrated light at all ages. The near-infrared spectral range is especially interesting since in the presence of an intermediate-age population, AGB stars are the main contributors. In this letter, we measure the near-infrared indices NaI and D$_{\rm CO}$ for a sample of 12 early-type galaxies in low density environments and compare them with the Fornax galaxy sample presented by Silva et al. (2008). The analysis of these indices in combination with Lick/IDS indices in the optical range reveals i) the NaI index is a metallicity indicator as good as C4668 in the optical range, and ii) D$_{\rm CO}$ is a tracer of intermediate-age stellar populations. We find that low-mass galaxies in low density environments show higher NaI and D$_{\rm CO}$ than those located in Fornax cluster, which points towards a late stage of star formation for the galaxies in less dense environments, in agreement with results from other studies using independent methods., 7 pages, 3 figures, accepted for publication in ApJL
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- 2009
11. RED SUPERGIANTS IN THE ANDROMEDA GALAXY (M31)
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Philip Massey, Geoffrey C. Clayton, Bertrand Plez, David R. Silva, Emily M. Levesque, Georges Meynet, André Maeder, and Knut Olsen
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Physics ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Andromeda Galaxy ,Metallicity ,FOS: Physical sciences ,Local Group ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Astrophysics - Astrophysics of Galaxies ,Galaxy ,Photometry (optics) ,Stars ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,Astrophysics::Solar and Stellar Astrophysics ,Red supergiant ,Astrophysics::Earth and Planetary Astrophysics ,Stellar evolution ,Astrophysics::Galaxy Astrophysics ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
Red supergiants are a short-lived stage in the evolution of moderately massive stars (10-25Mo), and as such their location in the H-R diagram provides an exacting test of stellar evolutionary models. Since massive star evolution is strongly affected by the amount of mass-loss a star suffers, and since the mass-loss rates depend upon metallicity, it is highly desirable to study the physical properties of these stars in galaxies of various metallicities. Here we identify a sample of red supergiants in M31 (the most metal-rich of the Local Group galaxies) and derive their physical properties by fitting MARCS atmosphere models to moderate resolution optical spectroscopy, and from V-K photometry., Accepted for publication in the Astrophysical Journal
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- 2009
12. A New Approach to the Study of Stellar Populations in Early‐Type Galaxies:K‐Band Spectral Indices and an Application to the Fornax Cluster
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Mariya Lyubenova, Harald Kuntschner, and David R. Silva
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Physics ,Metallicity ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Sigma ,Velocity dispersion ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Galaxy ,Stars ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Fornax Cluster ,Astrophysics::Galaxy Astrophysics ,Galaxy cluster ,Open cluster - Abstract
New measurements of K-band spectral features are presented for eleven early-type galaxies in the nearby Fornax galaxy cluster. Based on these measurements, the following conclusions have been reached: (1) in galaxies with no signatures of a young stellar component, the K-band Na I index is highly correlated with both the optical metallicity indicator [MgFe]' and central velocity dispersion; (2) in the same galaxies, the K-band Fe features saturate in galaxies with sigma > 150 km/s while Na I (and [MgFe]') continues to increase; (3) [Si/Fe] (and possibly [Na/Fe]) is larger in all observed Fornax galaxies than in Galactic open clusters with near-solar metallicity; (4) in various near-IR diagnostic diagrams, galaxies with signatures of a young stellar component (strong Hbeta, weak [MgFe]') are clearly separated from galaxies with purely old stellar populations; furthermore, this separation is consistent with the presence of an increased number of M-giant stars (most likely to be thermally pulsating AGB stars); (5) the near-IR diagrams discussed here seem as efficient for detecting putatively young stellar components in early-type galaxies as the more commonly used age/metallicity diagnostic plots using optical indices (e.g Hbeta vs. [MgFe]')., 47 pages, 16 figures, ApJ accepted
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- 2008
13. Building International Indigenous People’s Partnerships for Community-Driven Health Initiatives
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Tanya R. Wahbe, Vicente E. Pilco Llagcha, Eduardo Jovel, David R. Silva García, and N. Rose Point
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Economic growth ,Ecology ,business.industry ,Health, Toxicology and Mutagenesis ,Environmental resource management ,Capacity building ,Participatory action research ,Community-based participatory research ,Indigenous ,Animal ecology ,Political science ,General partnership ,Traditional knowledge ,business ,Knowledge transfer - Abstract
In this article we present an international Indigenous people’s partnership project co-led by two Indigenous communities, Musqueam (Coast Salish, Canada) and Totoras (Quichua, Ecuador), as a community-driven health initiative. The Musqueam-Totoras partnership includes Indigenous organizations, universities, international agencies, government, and nongovernmental organizations to address Indigenous health concerns in both communities. Our collaborative approach provides a framework to (a) increase the development expertise of Indigenous people internationally, (b) increase skills among all participants, and (c) facilitate Indigenous knowledge mobilization and translation to promote cultural continuity. This international Indigenous people’s partnership between north and south reflects the diversity and commonalities of Indigenous knowledge, contributes to cultural revitalization, and minimizes the impact of assimilation, technology, and globalization. Indigenous people’s partnerships contribute to self-determination, which is a prerequisite to the building and maintenance of healthy communities and the promotion of social justice. The exchange of Indigenous knowledge upholds Indigenous values of respect, reciprocity, relevance, and responsibility. Given the history of colonization and the negligence of governments in the exercising of these values with respect to Indigenous communities, this contemporary exchange among Indigenous people in the Americas serves to reclaim these values and practices. International cooperation empowering Indigenous people and other marginalized groups has become fundamental for their advancement and participation in globalized economies. An international Indigenous people’s partnership provides opportunities for sharing cultural, historical, social, environmental, and economic factors impacting Indigenous health. These partnerships also create beneficial learning experiences in community-based participatory research and community-driven health initiatives, provide culturally sensitive research ethics frameworks, increase capacity building, and address basic human needs identified by participating communities.
- Published
- 2007
14. Variability of Kepler Solar-Like Stars Harboring Small Exoplanets
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David R. Silva, Mark E. Everett, Paula Szkody, Steve B. Howell, David R. Ciardi, and Mark S. Giampapa
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Physics ,010504 meteorology & atmospheric sciences ,Astronomy ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Planetary system ,01 natural sciences ,Kepler ,Exoplanet ,Radial velocity ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Planet ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,010303 astronomy & astrophysics ,Circumstellar habitable zone ,Astrophysics::Galaxy Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,0105 earth and related environmental sciences - Abstract
We examine Kepler light curve variability on habitable zone transit timescales for a large uniform sample of spectroscopically studied Kepler exoplanet host stars. The stars, taken from Everett et al. (2013) are solar-like in their properties and each harbors at least one exoplanet (or candidate) of radius $\le$2.5\re. The variability timescale examined is typical for habitable zone planets orbiting solar-like stars and we note that the discovery of the smallest exoplanets ($\le$1.2\re) with corresponding transit depths of less than $\sim$0.18 mmag, occur for the brightest, photometrically quietest stars. Thus, these detections are quite rare in $Kepler$ observations. Some brighter and more evolved stars (subgiants), the latter which often show large radial velocity jitter, are found to be among the photometrically quietest solar-like stars in our sample and the most likely small planet transit hunting grounds. The Sun is discussed as a solar-like star proxy to provide insights into the nature and cause of photometric variability. It is shown that $Kepler's$ broad, visible light observations are insensitive to variability caused by chromospheric activity that may be present in the observed stars., Comment: Accepted in AJ
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- 2015
- Full Text
- View/download PDF
15. Preparing for the era of ELTs: precursor surveys, coordinated campaigns and operations planning
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Stephen Strom, Jeremy Mould, and David R. Silva
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Engineering management ,Geography ,Space and Planetary Science ,Management science ,Astronomy and Astrophysics - Published
- 2005
16. The Distance and Metallicity of the Newly Discovered, Nearby Irregular Galaxy HIZSS 3
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Philip Massey, P. A. Henning, David R. Silva, and Kathleen DeGioia-Eastwood
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Physics ,H II region ,010504 meteorology & atmospheric sciences ,Stellar population ,Milky Way ,Metallicity ,Astrophysics (astro-ph) ,Extinction (astronomy) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,01 natural sciences ,Galaxy ,Red-giant branch ,Space and Planetary Science ,0103 physical sciences ,Irregular galaxy ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
HIZSS3 is an H I source in the Zone of Avoidance. Its radio characteristics are consistent with it being nearby (~ 1.8 Mpc) low-mass dwarf irregular (dIm) galaxy. It contains a modest H II region, but its stellar population has not been resolved by optical observations. MMT spectra of the H II region are used to derive the line-of-sight extinction (E(B-V) = 1.41 +/- 0.04) and gas metallicity (log O/H + 12 ~ 7.8). ESO VLT near-IR images clearly reveal a resolved stellar population. Narrow-band Pbeta images of the H II region are used in combination with previously published Halpha data to obtain an independent line-of-sight extinction estimate: E(B-V) = 1.32 +/- 0.04. The adopted foreground extinction is E(B-V) = 1.36 +/- 0.06. Based on the K-band luminosity function and K,J-K color-magnitude diagram, the apparent magnitude and color of the tip of the red-giant branch (TRGB) are derived. In turn, these parameters are combined with the adopted foreground extinction to estimate the distance (1.69 +/- 0.07 Mpc) and mean red giant branch metallicity ([Fe/H] = -0.5 +/- 0.1). As an ensemble, these new observations significantly strengthen the conclusion that HIZSS3 is a newly discovered low-mass dIm lurking behind the Milky Way in the outskirts of the Local Group., Comment: Accepted, scheduled for ApJ, 10 Apr 05, V623 ; 14 pages
- Published
- 2005
17. A Wide-Field, Broadband Imaging Survey of Butcher-Oemler Cluster Cl 0024+1654: The Catalog
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Michael J. Pierce, A. Alexov, and David R. Silva
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Luminous infrared galaxy ,Physics ,education.field_of_study ,Population ,Astronomy ,Velocity dispersion ,Astronomy and Astrophysics ,Astrophysics ,Space and Planetary Science ,Galaxy group ,Elliptical galaxy ,Brightest cluster galaxy ,education ,Galaxy cluster ,Dwarf galaxy - Abstract
Wide-field (20' × 20') UBVI images of intermediate-redshift (z = 0.39), Butcher-Oemler cluster Cl 0024+1654 have been obtained. These data probe the rest-frame mid-UV properties over a much larger area than previous studies of Cl 0024+1654. Using these data, a multicolor catalog of nonstellar objects, assumed to be galaxies, has been constructed and analyzed. Using statistical arguments, the observed galaxy sample is separated into field and cluster populations. The basic photometric properties of these populations are presented and discussed. The "dropout" objects (i.e., objects undetected in one or more photometric bands) in our catalog are also discussed. A description of the final UBVI images, as well as the object catalog, is provided in an appendix. In a second appendix the use of SExtractor in crowded fields, such as the core of Cl 0024+1654, is discussed. The specific issues of the mid-UV properties of red envelope cluster galaxies, as well as the possible detection of a faint blue cluster population, are discussed in a forthcoming companion paper by Silva, Alexov, & Pierce.
- Published
- 2003
18. Long period variables in NGC 5128
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David R. Silva, Dante Minniti, and Marina Rejkuba
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Physics ,Astrophysics (astro-ph) ,Centaurus A ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Light curve ,Photometry (optics) ,symbols.namesake ,Amplitude ,Space and Planetary Science ,Fourier analysis ,symbols ,Elliptical galaxy ,Halo ,Variable star ,Astrophysics::Galaxy Astrophysics - Abstract
The first variable star catalogue in a giant elliptical galaxy NGC 5128 (Centaurus A) is presented. Using multi-epoch observations with ISAAC at the VLT we have detected 1504 red variables in two halo fields covering 10.46 arcmin square. For the variables with at least 10 good measurements, periods and amplitudes were determined using Fourier analysis and non-linear sine-curve fitting algorithms. The final catalogue contains 1146 long period variables with well established light curve parameters. Periods, amplitudes, JsHKs photometry as well as individual Ks-band magnitudes are provided for all the variables. The distribution of amplitudes ranges from 0.3 to a few magnitudes in the Ks-band, with a median value around 0.7 mag. The amplitudes, mean magnitudes and periods indicate that the majority of variables belong to the class of long period variables with semiregular and Mira variables. Exhaustive simulations were performed in order to assess the completeness of our catalogue and the accuracy of the derived periods., Comment: 14 pages, 14 figures; Some figures are highly compressed. For a full resolution version see http://www.eso.org/~mrejkuba/cenA_LPVs_cat.ps This is a complete version of the article to appear in the electronic version of A&A. A&A accepted
- Published
- 2003
19. H0 measurement from VLT deep I–band surface brightness fluctuations in NGC 564 and NGC 7619
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M. Scodeggio, Simona Mei, David R. Silva, and Peter J. Quinn
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Physics ,I band ,Very Large Telescope ,Surface brightness fluctuation ,Cosmic distance ladder ,Astronomy and Astrophysics ,Astrophysics ,Galaxy ,symbols.namesake ,Distance measurement ,Space and Planetary Science ,symbols ,Surface brightness ,Hubble's law - Abstract
We have measured the Hubble constant Ho in NGC 564 at cz ~ 5800 km/s and in NGC 7619 at cz ~ 3700 km/s with deep I-band Surface Brightness Fluctuation distance measurements at the ESO Very Large Telescope (VLT). We obtain Ho = 70 +/- 7 +/- 6 km/s/Mpc for NGC 564 and Ho = 68 +/- 6 +/- 6 km/s/Mpc for NGC 7619. The actual SBF sample used for the measurement of Ho in the Hubble Space Telescope Key Project on the Extragalactic Distance Scale (Freedman et al. 2001) amounts to six galaxies. When we combine the measurements from this work with our previous VLT I-band SBF distance measurement in IC 4296 (Mei et al. 2000), we obtain : Ho = 68 +/- 5 +/- 6 km/s/Mpc. When we add the Freedman et al. (2001) SBF sample, we obtain Ho = 71 +/- 4 +/- 6 km/s/Mpc.
- Published
- 2003
20. Radio‐Optical Alignment and Recent Star Formation Associated with Ionized Filaments in the Halo of NGC 5128 (Centaurus A)
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Dante Minniti, David R. Silva, F. Courbin, and Marina Rejkuba
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Physics ,Active galactic nucleus ,Star formation ,Radio galaxy ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,Centaurus A ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Galaxy ,Stars ,Space and Planetary Science ,Blue supergiant ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Halo ,Astrophysics::Galaxy Astrophysics - Abstract
We used the direct CCD camera at the Magellan I telescope at Las Campanas Observatory and FORS1 at Antu VLT at ESO Paranal Observatory to image fields centered on the inner and outer optical filaments in the halo of NGC 5128. In the V vs. U-V color-magnitude diagrams we have identified young blue supergiants associated with these line-emitting filaments located between the inner radio lobe and the northern middle lobe. Around the outer filament stars as young as 10 Myr were detected. They are principally aligned with the direction of the radio jet, but a vertical north-east alignment along the edge of the HI cloud is also present. Young stars in the inner filament field are found inside the bright knots of photoionized gas and are strongly aligned in the direction towards the center of the galaxy at the same position angle as the inner radio jet. Fitting the Padova isochrones on UV color-magnitude diagrams we find that the blue stars around the inner filaments have ages similar to the ones around the outer filaments ~10-15 Myr and the same abundance of Z=0.004. The presence of young blue supergiants clearly shows that the bright blue knots in the north-eastern halo of NGC 5128 are associations of young stars with photoionized gas. The temperature of the brightest stars is T \~ 12000-16000 K, insufficient to account alone for the high excitation lines observed in the surrounding ionized gas. Thus the optical emission jet is principally seen due to its alignment with the radio structure of the AGN. The highly collimated star formation is present only in the north eastern halo of the galaxy, suggesting the interaction of the jet with the gas clouds deposited during the last accretion event as the preferred triggering mechanism. (abridged), 10 pages, 5 figures; to be published in ApJ, v565 n1, January 20, 2002 issue
- Published
- 2002
21. The NOAO Data Laboratory: a conceptual overview
- Author
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Elizabeth Stobie, Mark Dickinson, Brian Thomas, Robert A. Swaters, Frossie Economou, A. Saha, J. Michael Fitzpatrick, Timothy C. Beers, Francisco Valdes, David R. Silva, Knut Olsen, Robert L. Seaman, and P. Norris
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World Wide Web ,Scope (project management) ,Work (electrical) ,Computer science ,business.industry ,Plan (drawing) ,business ,Data science ,Publication - Abstract
The NOAO Data Lab will allow users to efficiently utilize catalogs of billions of objects, augment traditional telescope imaging and spectral data with external archive holdings, publish high level data products of their research, share custom results with collaborators and experiment with analysis toolkits. The goal of the Data Lab is to provide a common framework and workspace for science collaborations and individuals to use and disseminate data from large surveys. In this paper we describe the motivations behind the NOAO Data Lab and present a conceptual overview of the activities we plan to support. Specific science cases will be used to develop a prototype framework and tools, allowing us to work directly with scientists from survey teams to ensure development will remain focused on scientifically productive tasks. This will additionally develop a pool of both scientific and technical experts who can provide ongoing advice and support for community users as the scope and capabilities of the Data Lab expand.
- Published
- 2014
22. High-resolution Multi-band Imaging for Validation and Characterization of Small Kepler Planets
- Author
-
David R. Silva, Elliott P. Horch, Mark E. Everett, Steve B. Howell, Thomas Barclay, Justin R. Crepp, and David R. Ciardi
- Subjects
Physics ,Earth and Planetary Astrophysics (astro-ph.EP) ,Astronomy ,FOS: Physical sciences ,Astronomy and Astrophysics ,Planetary system ,Light curve ,Photometry (astronomy) ,Stars ,Space and Planetary Science ,Planet ,Kepler object of interest ,Astrophysics::Solar and Stellar Astrophysics ,Transit (astronomy) ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Galaxy Astrophysics ,Astrophysics - Earth and Planetary Astrophysics ,Eclipse - Abstract
High-resolution ground-based optical speckle and near-infrared adaptive optics images are taken to search for stars in close angular proximity to host stars of candidate planets identified by the NASA Kepler Mission. Neighboring stars are a potential source of false positive signals. These stars also blend into Kepler light curves, affecting estimated planet properties, and are important for an understanding of planets in multiple star systems. Deep images with high angular resolution help to validate candidate planets by excluding potential background eclipsing binaries as the source of the transit signals. A study of 18 Kepler Object of Interest stars hosting a total of 28 candidate and validated planets is presented. Validation levels are determined for 18 planets against the likelihood of a false positive from a background eclipsing binary. Most of these are validated at the 99% level or higher, including 5 newly-validated planets in two systems: Kepler-430 and Kepler-431. The stellar properties of the candidate host stars are determined by supplementing existing literature values with new spectroscopic characterizations. Close neighbors of 7 of these stars are examined using multi-wavelength photometry to determine their nature and influence on the candidate planet properties. Most of the close neighbors appear to be gravitationally-bound secondaries, while a few are best explained as closely co-aligned field stars. Revised planet properties are derived for each candidate and validated planet, including cases where the close neighbors are the potential host stars., Comment: in press at AJ, 44 pages, 8 figures; The only changes made relative to version 1 are updates to the list of references
- Published
- 2014
- Full Text
- View/download PDF
23. Followup Observations of SDSS and CRTS Candidate Cataclysmic Variables
- Author
-
David R. Silva, Arlo U. Landolt, Stephanie Vasquez-Soltero, Mark E. Everett, Steve B. Howell, Howard E. Bond, and Paula Szkody
- Subjects
media_common.quotation_subject ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Spectral line ,Photometry (optics) ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,media_common ,Physics ,AM Herculis ,010308 nuclear & particles physics ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy and Astrophysics ,Orbital period ,Amplitude ,Astrophysics - Solar and Stellar Astrophysics ,13. Climate action ,Space and Planetary Science ,Sky ,Velocity amplitude ,Polar - Abstract
We present photometry of 11 and spectroscopy of 35 potential cataclysmic variables from the Sloan Digital Sky Survey, the Catalina Real-Time Transient Survey and vsnet-alerts. The photometry results include quasi-periodic oscillations during the decline of V1363 Cyg, nightly accretion changes in the likely Polar (AM Herculis binary) SDSS J1344+20, eclipses in SDSS J2141+05 with an orbital period of 76+/-2 min, and possible eclipses in SDSS J2158+09 at an orbital period near 100 min. Time-resolved spectra reveal short orbital periods near 80 min for SDSS J0206+20, 85 min for SDSS J1502+33, and near 100 min for CSS J0015+26, RXS J0150+37, SDSS J1132+62, SDSS J2154+15 and SDSS J2158+09. The prominent HeII line and velocity amplitude of SDSS J2154+15 are consistent with a Polar nature for this object, while the lack of this line and a low velocity amplitude argue against this classification for RXS J0150+37. Single spectra of 10 objects were obtained near outburst and the rest near quiescence, confirming the dwarf novae nature of these objects., Comment: 34 pages, 14 figures, in press at AJ
- Published
- 2014
- Full Text
- View/download PDF
24. HighK-band surface brightness fluctuations in NGC 1427 and NGC 720
- Author
-
David R. Silva, Simona Mei, M. Kissler–Patig, and Peter J. Quinn
- Subjects
Physics ,education.field_of_study ,Stellar population ,Population ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Galaxy ,Hubble sequence ,symbols.namesake ,Space and Planetary Science ,symbols ,Surface brightness ,Anomaly (physics) ,education ,High-κ dielectric - Abstract
We have observed K{band Surface Brightness Fluctuations (SBF) in NGC 1427 and NGC 720. We combine our measurements with distance measurements based on I{band SBF distance moduli and distance moduli derived by other distance indicators. When using distances from I{band SBF, we obtain MK = 6:55 0:27 for NGC 1427 and MK = 6:430:18 for NGC 720. When using an average of direct distance measurements, we obtain MK = 6:17 0:23 for NGC 1427 and MK = 6:14 0:24 for NGC 720. For both galaxies, MK lies well above the average value used as a calibration for distance indication (MK = 5:61 0:12 Jensen et al. 1998). In NGC 720 the high K{band SBF are most probably due to an intermediate-age population. However, there is no hint from current data for any anomaly in the stellar population of NGC 1427. These large variations of MK in several galaxies underline once more the need for a better understanding of MK as a function of stellar population properties (Mei et al. 2001b; Liu et al. 2001), especially with respect to the potential presence of intermediate{age populations.
- Published
- 2001
25. ESO Imaging Survey
- Author
-
E.R. Deul, Isabella Prandoni, R. Slijkhuis, M. Scodeggio, Mario Nonino, R. Wichmann, M. D. Guarnieri, Andreas Wicenec, R. Mendez, da L. Costa, L.F. Olsen, R. Hook, I. M. Hook, C. Benoist, Sandra Savaglio, David R. Silva, T. Erben, E. Bertin, and W. Freudling
- Subjects
Physics ,Reduction (complexity) ,Pixel ,Member states ,General Physics and Astronomy ,Survey data collection ,Astronomy ,Astrophysics ,Public survey ,Object (computer science) ,Pipeline (software) ,Reliability (statistics) - Abstract
This paper presents the first data evaluation of the ESO Imaging Survey (EIS), a public survey being carried out by ESO and member states, in preparation for the VLT first-light. The survey goals, organization, strategy and observations are discussed and an overview is given of the survey pipeline developed to handle EIS data and produce object catalogs. A report is presented on moderately deep I -band observations obtained in the first of four patches surveyed, covering a region of 3.2 square degrees centered at and . The products available to the community, including pixel maps (with astrometric and photometric calibrations) and the corresponding object catalogs, are also described. In order to evaluate the quality of the data, preliminary estimates are presented for the star and galaxy number counts, and for the angular two-point correlation function obtained from the available data. The present work is meant as a preview of the final release of the EIS data that will become available later this year.
- Published
- 1999
26. The Ages of Disturbed Field Elliptical Galaxies. II. Central Properties
- Author
-
Gregory D. Bothun and David R. Silva
- Subjects
Physics ,Field (physics) ,Space and Planetary Science ,Star formation ,Primary (astronomy) ,Elliptical galaxy ,Astronomy ,Asymptotic giant branch ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Astrophysics::Galaxy Astrophysics ,Galaxy - Abstract
The formation of elliptical galaxies via the merger of gas-rich disks has received considerable attention in recent years, with many studies strongly supporting the merger hypothesis. When investigated in detail, the dynamics of a major merger that produces a high phase-space density of material (e.g., the center of an elliptical galaxy) invariably produces the ubiquitous signature of a centrally concentrated burst of star formation. We have searched for this central burst of star formation in a sample of field elliptical galaxies that exhibit morphological fine structure thought to be indicative of merging. Out of this sample of 32 galaxies, we find only two galaxies, NGC 3610 and NGC 5322, with sufficiently red central near-IR colors to be consistent with the asymptotic giant branch light reflective of the central burst of star formation a few gigayears ago. Using NGC 3610 and 5322 as case studies, we discuss possible astrophysical links between global and central properties and their implied constraints on elliptical galaxy formation and evolution. In particular, we conclude that the available evidence argues against mergers of disk galaxies within the last 3–4 Gyr as being the primary formation mechanism for morphologically disturbed field elliptical galaxies.
- Published
- 1998
27. The Ages of Disturbed Field Elliptical Galaxies. I. Global Properties
- Author
-
David R. Silva and Gregory D. Bothun
- Subjects
Space and Planetary Science ,Astronomy and Astrophysics - Published
- 1998
28. Spectroscopy of Faint Kepler Mission Exoplanet Candidate Host Stars
- Author
-
Steve B. Howell, Mark E. Everett, Paula Szkody, and David R. Silva
- Subjects
Physics ,Earth and Planetary Astrophysics (astro-ph.EP) ,Metallicity ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Planetary system ,Exoplanet ,Astronomical spectroscopy ,Spectral line ,Stars ,Photometry (astronomy) ,Space and Planetary Science ,Planet ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Galaxy Astrophysics ,Astrophysics - Earth and Planetary Astrophysics - Abstract
Stellar properties are measured for a large set of Kepler Mission exoplanet candidate host stars. Most of these stars are fainter than 14th magnitude, in contrast to other spectroscopic follow-up studies. This sample includes many high-priority Earth-sized candidate planets. A set of model spectra are fitted to R~3000 optical spectra of 268 stars to improve estimates of Teff, log(g), and [Fe/H] for the dwarfs in the range 4750K5200K, includes a greater number of relatively evolved stars with larger radii than assumed by the mission on the basis of multi-color broadband photometry. About 26% of the modelled stars require radii to be revised upwards by a factor of 1.35 or greater, and modelling of 87% of the stars suggest some increase in radius. The sample presented here also exhibits a change in the incidence of planets larger than 3-4 Earth radii as a function of metallicity. Once [Fe/H] increases to >=-0.05, large planets suddenly appear in the sample while smaller planets are found orbiting stars with a wider range of metallicity. The modelled stellar spectra, as well as an additional 84 stars of mostly lower effective temperatures, are made available to the community., Comment: 39 pages, 10 figures
- Published
- 2013
29. Introduction to Telescopes
- Author
-
Ian S. McLean and David R. Silva
- Subjects
Physics - Published
- 2013
30. KEPLER-21b: A 1.6 R Earth PLANET TRANSITING THE BRIGHT OSCILLATING F SUBGIANT STAR HD 179070
- Author
-
Steve B. Howell, Jason F. Rowe, Stephen T. Bryson, Samuel N. Quinn, Geoffrey W. Marcy, Howard Isaacson, David R. Ciardi, William J. Chaplin, Travis S. Metcalfe, Mario J. P. F. G. Monteiro, Thierry Appourchaux, Sarbani Basu, Orlagh L. Creevey, Ronald L. Gilliland, Pierre-Olivier Quirion, Denis Stello, Hans Kjeldsen, Jörgen Christensen-Dalsgaard, Yvonne Elsworth, Rafael A. García, Günter Houdek, Christoffer Karoff, Joanna Molenda-Żakowicz, Michael J. Thompson, Graham A. Verner, Guillermo Torres, Francois Fressin, Justin R. Crepp, Elisabeth Adams, Andrea Dupree, Dimitar D. Sasselov, Courtney D. Dressing, William J. Borucki, David G. Koch, Jack J. Lissauer, David W. Latham, Lars A. Buchhave, Thomas N. Gautier, Mark Everett, Elliott Horch, Natalie M. Batalha, Edward W. Dunham, Paula Szkody, David R. Silva, Ken Mighell, Jay Holberg, Jerôme Ballot, Timothy R. Bedding, Hans Bruntt, Tiago L. Campante, Rasmus Handberg, Saskia Hekker, Daniel Huber, Savita Mathur, Benoit Mosser, Clara Régulo, Timothy R. White, Jessie L. Christiansen, Christopher K. Middour, Michael R. Haas, Jennifer R. Hall, Jon M. Jenkins, Sean McCaulif, Michael N. Fanelli, Craig Kulesa, Don McCarthy, Christopher E. Henze, Department of Earth and Planetary Science [UC Berkeley] (EPS), University of California [Berkeley], University of California-University of California, Infrared Processing and Analysis Center (IPAC), California Institute of Technology (CALTECH), Department of Psychology, St John's University, Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National University of Singapore (NUS), Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre de recherche de l'Institut universitaire de gériatrie de Montreal (CRIUGM), Université de Montréal (UdeM), Stellar Astrophysics Centre [Aarhus] (SAC), Aarhus University [Aarhus], School of Physics and Astronomy [Birmingham], University of Birmingham [Birmingham], Research institute of Computer Vision and Robotics [Girona] (VICOROB), Universitat de Girona (UdG), School of Physics and Astronomy, Astronomical Institute [Wroclaw], University of Wrocław [Poland] (UWr), Laboratoire Gemini (LG), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS), NASA Ames Research Center (ARC), Niels Bohr Institute [Copenhagen] (NBI), Faculty of Science [Copenhagen], University of Copenhagen = Københavns Universitet (KU)-University of Copenhagen = Københavns Universitet (KU), Jet Propulsion Laboratory (JPL), California Institute of Technology (CALTECH)-NASA, Geology Center of the University of Porto (CGUP), CGUP, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Sydney Institute for Astronomy (SIfA), The University of Sydney, Cognition, Langues, Langage, Ergonomie (CLLE-ERSS), Université Bordeaux Montaigne-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Toulouse - Jean Jaurès (UT2J)-Centre National de la Recherche Scientifique (CNRS), Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Instituto de Astrofisica de Canarias (IAC), Low Energy Astrophysics (API, FNWI), National Optical Astronomy Observatory (NOAO), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, University of California [Berkeley] (UC Berkeley), University of California (UC), University of California (UC)-University of California (UC), Department of Space Studies [Boulder], Southwest Research Institute [Boulder] (SwRI), Universidade do Porto = University of Porto, Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Universidad de La Laguna [Tenerife - SP] (ULL), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH), NASA-California Institute of Technology (CALTECH), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Toulouse - Jean Jaurès (UT2J), and Université de Toulouse (UT)-Université de Toulouse (UT)-Université Bordeaux Montaigne (UBM)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
010504 meteorology & atmospheric sciences ,Star (game theory) ,FOS: Physical sciences ,Astrophysics ,stars: interiors ,01 natural sciences ,techniques: photometric ,Planet ,stars: activity ,0103 physical sciences ,stars: oscillations (including pulsations) ,Transit (astronomy) ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,ComputingMilieux_MISCELLANEOUS ,0105 earth and related environmental sciences ,Physics ,[PHYS]Physics [physics] ,Subgiant ,Image (category theory) ,stars: late-type ,stars: magnetic field ,Astronomy and Astrophysics ,Light curve ,stars: individual (HD 179070: KIC 3632418) ,Exoplanet ,Planetary systems ,Orbit ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] - Abstract
We present Kepler observations of the bright (V=8.3), oscillating star HD 179070. The observations show transit-like events which reveal that the star is orbited every 2.8 days by a small, 1.6 R_Earth object. Seismic studies of HD 179070 using short cadence Kepler observations show that HD 179070 has a frequencypower spectrum consistent with solar-like oscillations that are acoustic p-modes. Asteroseismic analysis provides robust values for the mass and radius of HD 179070, 1.34{\pm}0.06 M{\circ} and 1.86{\pm}0.04 R{\circ} respectively, as well as yielding an age of 2.84{\pm}0.34 Gyr for this F5 subgiant. Together with ground-based follow-up observations, analysis of the Kepler light curves and image data, and blend scenario models, we conservatively show at the >99.7% confidence level (3{\sigma}) that the transit event is caused by a 1.64{\pm}0.04 R_Earth exoplanet in a 2.785755{\pm}0.000032 day orbit. The exoplanet is only 0.04 AU away from the star and our spectroscopic observations provide an upper limit to its mass of ~10 M_Earth (2-{\sigma}). HD 179070 is the brightest exoplanet host star yet discovered by Kepler., Comment: Accepted to ApJ
- Published
- 2012
31. Front Matter for Volume 7737
- Author
-
B. Thomas Soifer, David R. Silva, and Alison B. Peck
- Subjects
Volume (thermodynamics) ,Mechanics ,Geology ,Front (military) - Published
- 2010
32. Front Matter: Volume 7016
- Author
-
Roger Brissenden and David R. Silva
- Subjects
Volume (thermodynamics) ,Mechanics ,Geology ,Front (military) - Published
- 2008
33. Thirty Meter Telescope: observatory software requirements, architecture, and preliminary implementation strategies
- Author
-
David R. Silva, Thang Trinh, Corinne Boyer, Mark J. Sirota, and George Z. Angeli
- Subjects
business.industry ,Computer science ,Active optics ,Laser ,law.invention ,Primary mirror ,Telescope ,Observatory ,law ,Extremely Large Telescope ,Telescope mount ,Software requirements ,business ,Adaptive optics ,Software architecture ,Computer hardware ,Simulation ,Thirty Meter Telescope - Abstract
The Thirty Meter Telescope (TMT) will be a ground-based, 30-m optical-IR alt-az telescope with a highly segmented primary mirror located in a remote location. Efficient science operations require the asynchronous coordination of many different sub-systems including telescope mount, three independent active optics sub-systems, adaptive optics, laser guide stars, and user-configured science instrument. An important high-level requirement is target acquisition and observatory system configuration must be completed in less than 5 minutes (or 10 minutes if moving to a new instrument). To meet this coordination challenge and target acquisition time requirement, a distributed software architecture is envisioned consisting of software components linked by a service-based software communications backbone. A master sequencer coordinates the activities of mid-layer sequencers for the telescope, adaptive optics, and selected instrument. In turn, these mid-layer sequencers coordinate the activities of groups of sub-systems. In this paper, TMT observatory requirements are presented in more detail, followed by a description of the design reference software architecture and a discussion of preliminary implementation strategies.
- Published
- 2008
34. Thirty Meter Telescope: current operations concepts and plans
- Author
-
David R. Silva
- Subjects
Telescope ,Primary mirror ,Service (systems architecture) ,Computer science ,law ,Extremely Large Telescope ,Systems engineering ,Instrumentation (computer programming) ,Plan (drawing) ,Simulation ,Thirty Meter Telescope ,law.invention - Abstract
The Thirty Meter Telescope (TMT) will be a ground-based, 30-m optical-IR telescope with a highly segmented primary mirror located in a remote location. From the start of operations, TMT will provide a rich and diverse mix of seeing-limited and diffraction-limited instrumentation. Initially, only classical observing will be supported, although remote observing will follow almost immediately. Queue (or service) observing may be supported at a later date. TMT users will expect high facility uptime and observing efficiency as well as effective user support for planning and execution of observations. Those expectations are captured in the high-level Operations Concept Definition (OCD) document. The services and staffing needed to implement those concepts are described in the TMT Operations Plan. In this paper, high-level TMT operational concepts are summarized followed by a description of the current operations plan, including staffing model.
- Published
- 2008
35. Early light TMT instrumentation
- Author
-
David R. Silva, David Crampton, and Luc Simard
- Subjects
Physics ,Telescope ,Laser guide star ,law ,James Webb Space Telescope ,Near-infrared spectroscopy ,Systems engineering ,Field spectroscopy ,Instrumentation (computer programming) ,Adaptive optics ,Thirty Meter Telescope ,Remote sensing ,law.invention - Abstract
The Thirty Meter Telescope (TMT) project will provide diffraction limited and seeing limited capabilities that will be highly synergistic with JWST and other planned astronomy missions. TMT will thus be poised to tackle most of the questions confronting scientists today and for the next several decades. The early light instrumentation will provide NIR imaging and integral field spectroscopy designed to sample even the tiny 7mas images provided at 1.2 microns by a multi-conjugate laser guide star AO system, near-infrared multi-slit spectroscopy over a 2 arcmin field (fed by the same AO system, tuned for wide field performance), and wide field multi-object spectroscopy in the 0.3 - 1 micron wavelength region. TMT is being designed, as a system, to take advantage of the observational opportunities that a diffraction limited 30m telescope will afford. Results of detailed end-to-end modeling demonstrate excellent performance in both seeing-limited and diffraction-limited modes. TMT is also being designed to operate in a very efficient manner. Details of how this will be accomplished, descriptions of the planned instrumentation with focus on the early light instruments, new technologies that will be implemented, and a summary of the anticipated observing programs and how these will complement observations from other facilities are described.
- Published
- 2008
36. Central K-band kinematics and line strength maps of NGC 1399
- Author
-
David R. Silva, Mariya Lyubenova, and Harald Kuntschner
- Subjects
Physics ,Stellar population ,Astrophysics (astro-ph) ,Sigma ,Velocity dispersion ,FOS: Physical sciences ,Astronomy and Astrophysics ,Type-cD galaxy ,Astrophysics ,Radius ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Galaxy ,Space and Planetary Science ,Fornax Cluster ,Image resolution ,Astrophysics::Galaxy Astrophysics - Abstract
In this paper we present for the first time high spatial resolution K-band maps of the central kinematical and near-infrared spectral properties of the giant cD galaxy in the Fornax cluster, NGC 1399. We confirm the presence of a central velocity dispersion dip within radius < 0.2" seen in previous long-slit studies. Our velocity dispersion maps give evidence for a non-symmetric structure in this central area by showing three sigma peaks to the north-east, south-east and west of the galaxy centre. Additionally we measure near-IR line strength indices at unprecedented spatial resolution in NGC 1399. The most important features we observe in our 2-dimensional line strength maps are drops in Na I and CO(2-0) line strength in the nuclear region of the galaxy, coinciding spatially with the drop in sigma. The observed line strength and velocity dispersion changes suggest a scenario where the centre of NGC 1399 harbours a dynamically cold subsystem with a distinct stellar population., 9 pages, 5 figures, accepted for publication in A&A
- Published
- 2008
- Full Text
- View/download PDF
37. VLT service mode operations at seven years
- Author
-
Peter J. Quinn, David R. Silva, Fernando Comerón, Martino Romaniello, Gautier Mathys, Olivier Hainaut, Reinhard Hanuschik, and Andreas Kaufer
- Subjects
Scientific instrument ,Very Large Telescope ,Computer science ,business.industry ,media_common.quotation_subject ,Mode (statistics) ,Optical telescope ,law.invention ,Telescope ,law ,Astronomical interferometer ,Quality (business) ,Telecommunications ,business ,Simulation ,media_common - Abstract
The ESO Very Large Telescope (VLT) started operations on Cerro Paranal (Chile) in April 1999 with one Unit Telescope and two science instruments. Seven years later it is still a growing facility consisting of four 8.2-m telescopes, three auxiliary telescopes for interferometry, and 11 science instruments. In addition two dedicated survey telescopes with wide-field cameras, VST and VISTA, a fourth auxiliary telescope, and several new instruments will become available in the coming months. Since the very beginning, VLT operations were planned to contain a substantial component of Service Mode observing, amounting to approximately 50% of the available time. The success of the full-scale implementation of Service Mode operations is reflected nowadays by the steady increase in its demand by the community, both in absolute terms and also relative to the demand in Visitor Mode, by the highly positive feedback received from the users, and also by the increasing flow of scientific results produced by programs that have exploited the unique advantages of flexible short-term scheduling. It is also fulfilling the requirement of creating a science archive and populating it with a data stream having through a quality control process. Here we review the current status of Service Mode observing at the VLT and the VLT Interferometer (VLTI), the challenges posed by its implementation on a wide variety of instrument modes, and its strong requirement of an integrated, end-to-end approach to operations planning with adequate tools and carefully defined policies and procedures. The experience of these seven years of VLT operations have led to a thorough exploration of operations paradigms that will be essential to the scientific success of ALMA and the extremely large optical telescopes in the coming decades.
- Published
- 2006
38. Defining common software for the Thirty Meter Telescope
- Author
-
Kim Gillies, Jennifer Dunn, David R. Silva, Lewis, Hilton, and Bridger, Alan
- Subjects
Resource-oriented architecture ,Architecture domain ,business.industry ,Computer science ,Real-time computing ,Software ,Software deployment ,Middleware ,Component-based software engineering ,Software construction ,Software system ,Reference architecture ,Software verification and validation ,Software architecture ,Software engineering ,business ,Software architecture description ,Software design description - Abstract
The software for the Thirty Meter Telescope (TMT) is currently in the specification and design phase. A decision was made early on to provide a common software package that will provide basic infrastructure and services to be used by all project software packages. A roadmap for defining Common Software was written. The first roadmap step of defining what should be included in common software was accomplished by analyzing similar projects. The result was the definition of a reference architecture for end-to-end observatory software systems called the Observatory Software Domain Architecture. This architecture was then used to define the specifications for the TMT common software. This paper describes the roadmap, the reference architecture, and the current definition of TMT common software.
- Published
- 2006
39. Observatory software for the Thirty Meter Telescope (TMT)
- Author
-
Corinne Boyer, David R. Silva, Kim Gillies, Robert Marshall, Jennifer Dunn, P. N. Daly, Silva, David R., and Doxsey, Rodger E.
- Subjects
System requirements ,Engineering ,Software ,Observatory ,business.industry ,Systems engineering ,Software development ,Software design ,Software system ,Instrumentation (computer programming) ,business ,Thirty Meter Telescope ,Simulation - Abstract
SPIE Astronomical Telescopes + Instrumentation, 2006, Orlando, Florida, United States, Series: Proceedings of SPIE; no. 6270
- Published
- 2006
40. Deep VLT Imaging of NGC 5128
- Author
-
Dante Minniti, Timothy R. Bedding, David R. Silva, and Marina Rejkuba
- Subjects
Physics ,symbols.namesake ,symbols ,Astronomy ,Hubble sequence - Published
- 2006
41. Pulsation properties of C stars in the Small Magellanic Cloud
- Author
-
Marina Rejkuba, Gabriella Raimondo, David R. Silva, and Maria-Rosa L. Cioni
- Subjects
Physics ,Logarithm ,010308 nuclear & particles physics ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Light curve ,01 natural sciences ,Stars ,Amplitude ,Space and Planetary Science ,0103 physical sciences ,Magnitude (astronomy) ,Small Magellanic Cloud ,010303 astronomy & astrophysics - Abstract
A sample of carbon-rich stars (C-stars) in the Small Magellanic Cloud (SMC) was selected from the combined 2MASS and DENIS catalogues on the basis of their $J-K_s$ colour. This sample was extended to include confirmed C--stars from the Rebeirot et al. (1993) spectroscopic atlas. In this combined sample (N = 1152), a smaller number (N = 1079) were found to have MACHO observations. For this sub--sample, light curves were determined and 919 stars were found to have high quality light-curves with amplitudes of at least 0.05 mag. Of these stars, only 4% have a well--defined single period -- most of these have multiple well-defined periods, while 15% have highly irregular light--curves. The distribution of the logarithm of the period versus magnitude, colour, period ratio (if applicable), and amplitude was analyzed and compared with previous works. Variable C-stars are distributed in three sequences: B, C and D from Wood et al. (1999), and do not populate sequences with periods shorter than $\log P \sim 1.5$. Stellar ages and masses were estimated using stellar evolutionary models., Comment: 18 pages, 22 figures, 3 tables, A&A Accepted (2005 March 18), added a reference, corrected typos
- Published
- 2005
- Full Text
- View/download PDF
42. Observing with the VLT interferometer
- Author
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Andrea Richichi, S. Marteau, P. Nass, Fredrik T. Rantakyrö, Christian A. Hummel, Pascal Ballester, Markus Wittkowski, Tim Canavan, Mario van den Ancker, Sebastien Morel, Michele Peron, Andreas Kaufer, Isabelle Percheron, Fernando Comerón, Markus Schoeller, Gautier Mathys, Monika G. Petr-Gotzens, Anders Wallander, and David R. Silva
- Subjects
Physics ,Scientific instrument ,Very Large Telescope ,Astronomical optical interferometry ,MIDI ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy ,computer.file_format ,Service mode ,Interferometry ,Astronomical interferometer ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,computer ,Astrophysics::Galaxy Astrophysics ,Remote sensing - Abstract
The ESO Very Large Telescope Interferometer (VLTI) is the first general-user interferometer that offers near- and mid-infrared long-baseline interferometric observations in service mode as well as visitor mode to the whole astronomical community. Regular VLTI observations with the first scientific instrument, the mid-infrared instrument MIDI, have started in ESO observing period P73, for observations between April and September 2004. The efficient use of the VLTI as a general-user facility implies the need for a well-defined operations scheme. The VLTI follows the established general operations scheme of the other VLT instruments. Here, we present from a users' point of view the VLTI specific aspects of this scheme beginning from the preparation of the proposal until the delivery of the data.
- Published
- 2004
43. VLT end-to-end science operations: the first three years
- Author
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Fernando Comerón, David R. Silva, Roberto Gilmozzi, Gautier Mathys, Michele Peron, Benoit Pirenne, and Peter J. Quinn
- Subjects
Development environment ,Data flow diagram ,Service (systems architecture) ,End-to-end principle ,Computer science ,business.industry ,Visitor pattern ,Telecommunications ,business ,Service mode ,Remote sensing - Abstract
The end-to-end operations of the ESO VLT has now seen three full years of service to the ESO community. During that time its capabilities have grown to four 8.2m unit telescopes with a complement of four optical and IR multimode instruments being operated in a mixed Service Mode and Visitor Mode environment. The input and output of programs and data to the system is summarized over this period together with the growth in operations manpower. We review the difficulties of working in a mixed operations and development environment and the ways in which the success of the end-to-end approach may be measured. Finally we summarize the operational lessons learned and the challenges posed by future developments of VLT instruments and facilities such as interferometry and survey telescopes.
- Published
- 2002
44. Service mode scheduling at the ESO very large telescope
- Author
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David R. Silva
- Subjects
Very Large Telescope ,Computer science ,Observatory ,Real-time computing ,Operational efficiency ,Service mode ,Scheduling (computing) ,Remote sensing - Abstract
The execution of observations in Service Mode is an option at the European Southern Observatory Very Large Telescope. In this operations mode, observations are not scheduled for specific nights, they are scheduled flexibly. Each night observations are selected from a pool of possible observations based on Observing Programme Committee (OPC) priority and the current observing conditions. Ideally, the pool of possible observations contains a range of observations that exactly match the real range of conditions and the real number of available hours, so that all observations are completed in a timely manner. Since this ideal case never occurs, constructing the pool of observations must be done carefully, with the goals of maximizing scientific return and operational efficiency. In this paper, basic ESO Service Mode scheduling concepts are presented. A specific VLT focus is maintained for most of this article, but the general principles are true for all ESO facilities executing Service Mode runs.
- Published
- 2002
45. Quality Control of the ESO-VLT instruments
- Author
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David R. Silva, P. Sartoretti, W. Hummel, and Reinhard Hanuschik
- Subjects
Data flow diagram ,Measure (data warehouse) ,Very Large Telescope ,Observatory ,Computer science ,business.industry ,Web page ,Real-time computing ,Computer data storage ,Calibration ,business ,Pipeline (software) - Abstract
Currently four instruments are operational at the four 8.2m telescopes of the European Southern Observatory Very Large Telescope: FORS1, FORS2, UVES, and ISAAC. Their data products are processed by the Data Flow Operations Group (also known as QC Garching) using dedicated pipelines. Calibration data are processed in order to provide instrument health checks, monitor instrument performance, and detect problems in time. The Quality Control (QC) system has been developed during the past three years. It has the following general components: procedures (pipeline and post-pipeline) to measure QC parameters; a database for storage; a calibration archive hosting master calibration data; web pages and interfaces. This system is part of a larger control system which also has a branch on Paranal where quick-look data are immediately checked for instrument health. The VLT QC system has a critical impact on instrument performance. Some examples are given where careful quality checks have discovered instrument failures or non-optimal performance. Results and documentation of the VLT QC system are accessible under http://www.eso.org/qc/.
- Published
- 2002
46. First spectroscopic evidence for carbon stars outside the Local Group: properties of a massive star cluster in NGC 7252
- Author
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Martin Groenewegen, M. Mouhcine, Ariane Lançon, David R. Silva, and Claus Leitherer
- Subjects
Physics ,Stellar population ,Metallicity ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Giant star ,Carbon star ,Galaxy ,Stars ,Star cluster ,Space and Planetary Science ,Asymptotic giant branch ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
We present near-IR spectroscopy of the massive intermediate age star cluster W3 in the merger remnant galaxy NGC 7252, obtained with the NTT telescope. This cluster has an age when the integrated near-IR properties of a stellar population are dominated by the cool and luminous AGB stars. We compare the data with instantaneous curst model predictions from new evolutionary synthesis models that include: (1) the computation of the evolution through the TP-AGB for low- and intermediate-massive stars, with the initial mass and metallicity dependent formation of carbon stars; (2) spectroscopic data from a new stellar library in which differences betwenn static giants, vriable O-rich TPAGB stars and carbon stars are accounted for. The comparison of the data to the models clearly shows that carbon stars are present: for the first time, carbon star spectral features are thus detected directly outside the Local Group (abriged), Comment: Accepted for publication in A&A, 14 pages
- Published
- 2002
- Full Text
- View/download PDF
47. The X-shooter Spectral Library (XSL)
- Author
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David R. Silva, P. Prugniel, A. Vazdekis, Reynier Peletier, Yanping Chen, Ariane Lançon, Scott Trager, Anais Gonneau, Kapteyn Astronomical Institute, and Astronomy
- Subjects
stars: abundances ,Stellar population ,FOS: Physical sciences ,stars: AGB and post-AGB ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Type (model theory) ,Lambda ,Spectral line ,stars: atmospheres ,Astrophysics::Solar and Stellar Astrophysics ,Spectral resolution ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Physics ,Very Large Telescope ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy and Astrophysics ,Astrophysics - Astrophysics of Galaxies ,Galaxy ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,galaxies: stellar content ,stars: fundamental parameters ,Astrophysics::Earth and Planetary Astrophysics - Abstract
We present the first release of XSL, the X-Shooter Spectral Library. This release contains 237 stars spanning the wavelengths 3000--10200 \AA\ observed at a resolving power $R \equiv \lambda / \Delta\lambda \sim 10000$. The spectra were obtained at ESO's 8-m Very Large Telescope (VLT). The sample contains O -- M, long-period variable (LPV), C and S stars. The spectra are flux-calibrated and telluric-corrected. We describe a new technique for the telluric correction. The wavelength coverage, spectral resolution and spectral type of this library make it well suited to stellar population synthesis of galaxies and clusters, kinematical investigation of stellar systems and studying the physics of cool stars., Comment: 41 pages, 38 figures, 5 tables. Accepted for publication in A&A. Webpage: http://xsl.u-strasbg.fr/
- Published
- 2014
48. K-band versus I-band Surface Brightness Fluctuations as distance indicators
- Author
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Simona Mei, Peter J. Quinn, and David R. Silva
- Subjects
Physics ,Very Large Telescope ,I band ,Stellar population ,Astrophysics (astro-ph) ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Galaxy ,Space and Planetary Science ,K band ,Globular cluster ,Elliptical galaxy ,Astrophysics::Solar and Stellar Astrophysics ,Surface brightness ,Astrophysics::Galaxy Astrophysics - Abstract
We evaluate the method of optical and infrared Surface Brightness Fluctuations (SBF) as a distance indicator and its application on 8-m class telescopes, such as the Very Large Telescope (VLT). The novelty of our approach resides in the development of Monte Carlo simulations of SBF observations incorporating realistic elliptical galaxy stellar population models, the effects induced by globular clusters and background galaxies, instrumental noise, sky background and PSF blurring. We discuss, for each band and in different observational conditions, the errors on distance measurements arising from stellar population effects, data treatment and observational constraints. With 8-m class telescopes, one can extend I-band SBF measurements out to 6000-10000 km/s. Integration times in the K-band are too expensive from the ground, due to the high infrared background for large-scale distance determination projects. Nevertheless ground-based K-band measurements are necessary to understand stellar population effects on the SBF calibration, and to prepare future space-based observations, where this band is more efficient., A&A, in press, 17 pages, 10 figures
- Published
- 2001
49. Stellar populations in NGC 5128 with the VLT: evidence for recent star formation
- Author
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David R. Silva, Timothy R. Bedding, Dante Minniti, and Marina Rejkuba
- Subjects
Physics ,education.field_of_study ,Stellar population ,Star formation ,Metallicity ,Population ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Galaxy ,Stars ,Space and Planetary Science ,Elliptical galaxy ,Astrophysics::Solar and Stellar Astrophysics ,Halo ,Astrophysics::Earth and Planetary Astrophysics ,education ,Astrophysics::Galaxy Astrophysics - Abstract
We resolve stars of the nearest giant elliptical galaxy NGC 5128 using VLT with FORS1 and ISAAC. We construct deep U, V and Ks color-magnitude and color-color diagrams in two different halo fields (in the halo and in the north-eastern diffuse shell). In the outer, shell field, at ~14 kpc from the center of the galaxy, there is a significant recent star formation with stars as young as 10 Myr, approximately aligned with the prominent radio and x-ray jet from the nucleus of the host AGN. Ionized gas filaments are evident in ultraviolet images near the area where neutral HI and CO molecular gas was previously observed. The underlying stellar population of the halo of the giant elliptical is predominantly old with a very broad metallicity distribution. The presence of an extended giant branch reaching M_bol=-5 mag suggests the existence of a significant intermediate-age AGB population in the halo of this galaxy., Comment: 18 pages, 18 figures; to be published in A&A; high res. version at http://www.eso.org/~mrejkuba/cenA_starsVLT.ps
- Published
- 2001
- Full Text
- View/download PDF
50. DIVISION IX: OPTICAL & INFRARED TECHNIQUES
- Author
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Jayant Murthy, Eugene F. Milone, Ian S. McLean, Rolf-Peter Kudritzki, Michael G. Burton, Andreas Quirrenbach, Guillermo Torres, Xiangqun Cui, Andrei Tokovinin, David R. Silva, Gražina Tautvaišiene, and Stephen T. Ridgway
- Subjects
Engineering ,Space and Planetary Science ,business.industry ,General assembly ,Library science ,Astronomy and Astrophysics ,Division (mathematics) ,business ,Cartography - Abstract
Division IX provides a forum for astronomers engaged in the planning, development, construction, and calibration of optical and infrared telescopes and instrumentation, as well as observational procedures including data processing. A few years ago, discussions were started about changes in the structure of Division IX, with the aim of bringing it more in line with today's world of large coordinated projects and multi-national observatories. The course of this process, and further steps to be taken in the period from 2009 to 2012, were at the focus of the deliberations at the business meeting of Division IX at the IAU General Assembly in Rio de Janeiro.
- Published
- 2010
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